Low PAPR Reference Signal Design for High Frequency Bands
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Solution Overview
Problem
Current reference signal designs for high-frequency bands, such as those above 52.6 GHz, face limitations in power efficiency due to high peak-to-average power ratio (PAPR), particularly for downlink transmissions in 5G NR systems, which affect channel estimation and spectral efficiency.
Innovation Solution
The proposed solution involves designing demodulation reference signals (DM-RS) and channel state information reference signals (CSI-RS) using low PAPR π/2 BPSK modulation with DFT-s-OFDM waveform, supporting comb structures for efficient multiplexing of multiple antenna ports, and employing orthogonal cover codes and sequence pairs to maintain ideal autocorrelation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CP-OFDM waveform is used for downlink transmission, then spectral efficiency is improved, but peak-to-average power ratio (PAPR) increases leading to reduced power efficiency
Solution Approach 1:
The patent applies parameter changes by switching the waveform type from CP-OFDM to DFT-s-OFDM for downlink reference signal transmission. This changes the fundamental modulation parameter, reducing PAPR while maintaining spectral efficiency through the use of DFT spreading followed by OFDM modulation, which inherently lowers peak power variations.
Solution Approach 2:
The patent segments the reference signal transmission by introducing multiple orthogonal cover codes (OCC) that divide the reference signal across different time-frequency resources. This segmentation allows the use of DFT-s-OFDM waveform with lower PAPR while maintaining the spectral efficiency benefits through proper resource allocation and multiplexing.
2Measurement precision
If conventional reference signal design is used for high frequency bands, then channel estimation can be performed, but power efficiency deteriorates due to high PAPR
Solution Approach 1:
The patent changes the waveform parameter from CP-OFDM to DFT-s-OFDM specifically for reference signal transmission in high frequency bands. This parameter change reduces PAPR and improves power efficiency while the orthogonal cover codes and sequence design maintain channel estimation precision through proper correlation properties.
Solution Approach 2:
The patent makes the reference signal design universal by creating a multi-functional solution that simultaneously achieves low PAPR for power efficiency and maintains channel estimation accuracy. The DFT-s-OFDM waveform with orthogonal cover codes serves multiple purposes: reducing peak power, enabling channel estimation, and supporting multiple antenna ports.
3Loss of energy
If DFT-s-OFDM waveform is used, then peak-to-average power ratio (PAPR) is reduced improving power efficiency, but spectral efficiency decreases compared to CP-OFDM
Solution Approach 1:
The patent segments the resource allocation by introducing orthogonal cover codes that divide reference signals across different time-frequency resources. This segmentation enables DFT-s-OFDM to achieve both low PAPR and improved spectral efficiency through better resource utilization and reduced interference between multiple antenna ports.
Solution Approach 2:
The patent adds another dimension to the reference signal design by introducing orthogonal cover codes in the time domain that work alongside the frequency domain OFDM modulation. This dimensional addition allows DFT-s-OFDM to achieve spectral efficiency comparable to or better than CP-OFDM while maintaining its low PAPR advantage.
4Reliability
If reference signals are transmitted for channel estimation, then communication reliability is improved, but power consumption increases due to high PAPR characteristics
Solution Approach 1:
The patent changes the fundamental waveform parameter from CP-OFDM to DFT-s-OFDM for reference signal transmission. This parameter change directly reduces PAPR and power consumption while maintaining communication reliability through the preservation of essential channel estimation functions via orthogonal cover codes and proper sequence design.
Solution Approach 2:
The patent converts the potential harm of high PAPR into a benefit by using DFT-s-OFDM's inherent low PAPR characteristic. The DFT spreading operation, which could be seen as adding complexity, actually reduces peak power variations and improves power efficiency while the orthogonal cover codes ensure reliable channel estimation is maintained.
Data Source
AI summary
Various embodiments herein provide techniques for reference signal (RS) configuration for high frequency bands (e.g., frequency above 52.6 GHz). For example, embodiments may include techniques for configuration of a demodulation reference signal (DM-RS), a channel state information reference signal (CSI-RS), and/or a sounding reference signal (SRS). The RS configuration may provide a low peak-to-average power ratio (PAPR) compared to prior techniques. Other embodiments may be described and claimed.